Modelling lifts lid on wheat yields

As the ENDURE scientists working on the WheatPest project note, European farmers growing winter wheat can have much to contend with, besides the vagaries of the weather. These include an array of potentially harmful pests, ranging from the damaging effects of weeds and aphids through to diseases such as Septoria tritici blotch, also known as brown and yellow rusts.

Until the creation of WheatPest, predicting the possible effects on wheat yields because of these pests was difficult, not least because wheat crops can be affected by a variety of different pests at different stages of the growing season.

Writing in the Elsevier journal Field Crops Research
, ENDURE scientists from France's Institut National de la Recherche Agronomique (French National Institute for Agricultural Research), reveal how WheatPest has been created to take account of these different pests and different wheat crop management regimes.

The concept of production situation

The authors note that the concept of production situation is a cornerstone for crop protection. The production situation is another way of describing the farmer's crop management approach which, in turn, is a reflection of his (or her) response to their economic, social and physical environment. The concept of production situation helps us to understand how neighbouring farms, or even two fields on the same farm, can produce crops that grow and develop very differently.

Once the production situation has been established, researchers can predict what is known as the attainable yield, in other words the yield of the crop if nothing hindered its growth (thereby discounting the influence of climatic disasters and pests). From this, the goal is to predict the actual yield, which in the case of WheatPest means the yield after the crop-reducing effects of a pest or combination of pests.

It has become possible to do this thanks to advances in our knowledge on pest life cycles. Pests may be diverse, but they fall into groups when it comes to how they damage or injure a crop.

Furthermore, pests and the injuries they cause are not a random occurrence, but patterns have been established which show that injuries caused by a given pest tend to be associated with other injuries. These are called injury profiles, which have been shown in several cases to be associated with production situations and, more particularly, with the crop management regime that is being followed.

Accurate estimations

So, scientists know how the crop will perform in a given situation and the injuries and damages that are likely to occur. The trick then is to translate these factors into a series of formulae which will produce an accurate estimate of the final yield. For WheatPest this crop is winter wheat, but the authors note that it would be relatively straightforward to apply similar calculations to spring wheat and incorporate other pests.

These kinds of new modelling approaches are an integral part of ENDURE's research activities and the authors note that the relationship between production situations and injury profiles has important implications for crop protection:

It indicates that crop management practices are key to explaining the varying combinations of pests that may affect a crop.

It suggests that changes in crop management and, therefore, in production situations, are likely to strongly influence the nature of injury profiles.

It opens the way for research into where pest management, integrated with crop management, might choose not to use unsustainable components, including heavy reliance on pesticides.